The picornavirus family includes rhinoviruses and enteroviruses, which cause approximately one half of common colds each year. Pleconaril is a new oral drug that has been shown to inhibit viral replication in about 90 percent of rhinovirus serotypes and more than 99 percent of enteroviruses. Hayden and colleagues investigated the efficacy and safety of pleconaril for treatment of the common cold by examining the results of two identical randomized, controlled, multicenter trials.

A total of 2,096 patients were recruited, based on self-reported cold symptoms of fewer than 24 hours' duration. Symptoms meriting inclusion were the presence of rhinorrhea and at least one other cold symptom (nasal congestion, sore throat, cough). Patients with fever, chronic cough, recent treatment for allergic rhinitis or asthma, immuno-deficiency, or major medical comorbidity, and women who were pregnant or nursing were excluded. Smokers were permitted in the trial.

Participants were randomized to receive pleconaril in a dosage of 400 mg three times daily for five days (1,046 patients) or a matching placebo (1,050 patients). Only acetaminophen or dextromethorphan were allowed during the study for symptom relief, to prevent possible masking of nasopharyngeal symptoms of colds. Follow-up was conducted by telephone every other day until cold resolution, or 18 days post-infection. The drop out rates among subjects in the placebo and drug treatment groups were 6.6 percent and 7.6 percent, respectively. Participants recorded the severity of six cold symptoms (rhinorrhea, nasal congestion, cough, malaise, sore throat, and myalgias) twice daily. Nasal mucus samples were evaluated at baseline and on study days 3 and 6 for picornavirus infection by polymerase chain reaction assay for viral DNA. Overall, picornavirus infection was documented by polymerase chain reaction in 65 percent of self-reported cold victims, and the rate did not differ significantly between placebo and pleconaril groups.

In both studies, treatment with pleconaril was associated with a shorter duration of cold symptoms in patients with documented picornavirus infection. The mean reduction in duration of cold symptoms was one day (6.3 days with treatment, 7.3 days with placebo). The severity of cold symptoms also was reduced in patients receiving pleconaril. Pleconaril was generally well tolerated, with only slight increases above placebo rates for headache, diarrhea, and nausea.

The authors conclude that the use of pleconaril within 24 hours of onset of the common cold was associated with a reduction in the duration and severity of cold symptoms.

editor's note: From arm's length, the figures confirm what may be obscured by the “significant”p values found scattered in the dense tables describing these large studies (i.e., not much difference between pleconaril and placebo). One would suspect that the reason for combining two identical trials was the borderline statistical significance of the first trial, and the questionable clinical significance (and cost) of converting a seven-day cold into a six-day process, while taking medication three times daily.—B.Z.